1. Field of the Invention
The present invention relates to a light source driving circuit and a controlling method thereof. More particularly, the present invention relates to a light source driving circuit to detect whether each light source works properly and short a failed one, and a controlling method thereof.
2. Description of Related Art
FIG. 1 shows a conventional backlight device. Referring to FIG. 1, the conventional backlight device includes a light-emitting module 105 and a resistor 107. When a power supply 103 provides a voltage for the light-emitting module 105 to operate, a working current I1 is generated and flows through the light-emitting module 105 and the resistor 107.
FIG. 2 shows another conventional backlight device. Referring to FIG. 2, the backlight device includes two light-emitting modules 202a, 202b, switches 205a, 205b, and a current mirror 209. One end of the light-emitting modules 202a, 202b is coupled to the power supply 103, and the other end is coupled to the current mirror 209 through the switches 205a, 205b respectively. When the power supply 103 provides a voltage for the light-emitting modules 202a, 202b to operate, and the switches 205a, 205b are turned on, so as to generate corresponding working currents I2, I3.
In FIGS. 1 and 2, the light-emitting modules 105, 202a, 202b include a plurality of serially-connected LEDs. However, as the LEDs may be shorted or break due to the processes or other factors, when one or more LEDs in the light-emitting module break, the light-emitting module cannot be lighted, and the overall brightness greatly decreases. Besides, when one or more LEDs in the light-emitting module are shorted, the overall brightness also decreases.